The running back position continues to be one of the more fascinating ones in the NFL and one that comes with great turnover every season. While some contend that it's one of the most replaceable spots in football, others will point to dominant seasons from several elite running backs this year as proof of what these players can add to a team. One item we can all agree on is that the position is rather fungible, and players that emerge for chapters of the season or even the entirety of a campaign may offer completely different outputs the next year.

The 2016 season brought us a host of new faces at the position and saw several more take the jump to the next level. All of these players experienced different degrees of defensive attention on their runs.

One of the Next Gen Stats we have here measures performance against stacked defensive fronts. This gives us a running back's yards per attempt on non-red zone carries when there are eight or more defenders in the box. The metric helps us get a sense of how a running back performed against crowded fronts, whether it be from extra defensive attention or the formations the offenses deploy. As with any stat, but especially this one, context is key and we'll attempt to dilute that context with each player.

Notes: Only running backs with 35 or more carries against eight-plus defenders in the box qualified for these rankings (19 total running backs). We'll also make reference to a few different personnel packages and formations here, so below is a guide if you need a refresher...11 personnel: one running backs, one tight end12 personnel: one running back, two tight ends21 personnel: two running backs, one tight end22 personnel: two running backs, two tight endsI-formation: Running backs lined up behind a fullback

1) Jay Ajayi, Miami Dolphins (6.36 yards per carry)

When Adam Gase left Jay Ajayi behind in Miami for a road trip to Seattle back in Week 1 literally no one could have predicted that he would go on to be the fourth-leading rusher in the NFL. The Dolphins were off to a 1-4 start before Ajayi's breakout 204-yard, two touchdown game in Week 6, an outing he outdid the next week by putting 214 rushing yards on the Bills. The aggressive Boise State product gave the Dolphins an identity, one in a physical mold that they never had in the Joe Philbin years.

One of the most powerful running backs in the NFL, Jay Ajayi broke tackles left and right this season while leaving defenders helpless in his wake. Naturally, as the year wore on, teams began to dedicate extra attention to Ajayi by stacking the box, but even that was not enough to slow him down. He managed an NFL-best 6.36 yards per carry against eight-plus man boxes, which he saw on 19.3 percent of his non-red zone carries. He became an expert at making the defense pay for crowding the line of scrimmage by getting loose into the secondary for big plays. Ajayi managed three runs of 20-plus yards when facing stacked boxes.

The Dolphins have to hope the long-term concerns regarding Ajayi's knee that caused him to fall to the fifth-round on draft day hold off a bit longer. They've stumbled onto, without question, one of the 10 best pure runners in the NFL.

2) Isaiah Crowell, Cleveland Browns (5.88 yards per carry)

Seeing Isaiah Crowell's name on this list might surprise some, as he finished shy of 1,000 yards in his third pro season. However, what this should remind us of is that Crowell is indeed quite a good player, the Browns just so rarely found themselves in a comfortable game script for sticking with the ground game. While the Browns only ranked 19th as a rushing offense this year, that looks a bit more impressive when you note that they ranked 30th in run play percentage.

Crowell faced an eight-plus man box on 23.8 percent of his non-red zone carries and averaged 5.88 yards per carry. He was quite adept at breaking off big plays against stacked fronts with six 15-plus yard runs, two of which went for over 20 yards and one for an 85-yard touchdown against Baltimore. The Browns were primarily a three-receiver offense, with 37.4 plays per game (60.9 percent) run out of the 11-personnel package and Crowell took most of his handoffs (71) out of the shotgun. With Cleveland's subpar quarterback play, it only made sense for defenders to dedicate extra resources to stopping the run. Crowell showed he could step up to that test, despite less than stellar offensive line play for much of the season.

3) LeSean McCoy, Buffalo Bills (5.48 yards per carry)

The Buffalo Bills led the NFL in rushing for the second straight season, and LeSean McCoy's strong performance against eight-men fronts is a big reason why. McCoy saw a stacked box on 21.4 percent of his non-red zone carries and averaged 5.48 yards per carry. He had seven runs of 10-plus yards, three of which went for 20 or more yards. The offense Buffalo runs will naturally bring more defenders into the box, especially with a mobile quarterback behind center. The Bills ranked 29th in plays run with three wide receivers on the field, and 51.1 percent of their plays coming out of 21, 12 or 22 personnel. Even as he's aging, McCoy still shows an ability to navigate a crowded front. Additionally, his backup Mike Gillislee saw an eight-plus man box on 38.6 percent of his 32 non-red zone carries and averaged 5.34 yards per carry.

4) Ezekiel Elliott, Dallas Cowboys (5.23 yards per carry)

Everyone knows of the vaunted Dallas rushing attack, and the Cowboys led the NFL this year in run play percentage with 49.4 percent. Naturally, running with that kind of frequency is going to bring extra defenders down to the line, and Ezekiel Elliott saw an eight-plus man box on 27.6 percent of his non-red zone carries this season, ninth-highest among running backs with 35-plus attempts. Dallas actually does a good job of aligning their personnel so that the defense cannot crowd the line, as the majority of their running plays (218) came with three wide receivers on the field. Another 159 came with two tight ends on the field, and Elliott likely faced most of his stacked boxes out of those plays.

One of the biggest debates that sprung out of the Cowboys taking Elliott at fourth overall was whether he was a necessary pick given that their running game was already productive last year. Darren McFadden took 30.6 percent of carries against eight-man boxes on non-red zone plays, which was 10th-highest among running backs (20-plus carries). The presence of Dak Prescott and his fast emergence as one of the NFL's most efficient passers likely contributed to a mostly negligible three percent differential between 2015 and 2016. While McFadden averaged a healthy 4.6 yards per carry on those runs, it's clear that Elliott adds a different dimension to the team. No running back produced more big plays against stacked fronts than the 2016 fourth-overall pick. He led all running backs in runs of 10-plus yards (12), 15-plus yards (eight) and 20-plus yards (five) when facing eight men in the box.

5) DeMarco Murray, Tennessee Titans (4.77 yards per carry)

DeMarco Murray faced an eight-man box on a whopping 40.2 percent of his 249 non-red zone carries this season. His bounce back season included a strong performance on those plays, averaging 4.77 yards per carry and taking 11 runs for more than 10 yards. What's notable here is that Derrick Henry also ran against an eight-man box on a league-high 48.9 percent of his non-red zone carries (3.67 yards per carry). While at first blush this seems like an indictment on Marcus Mariota and the passing game by the defensive coordinators they faced, this is an instance where context is key. The Titans rank 32nd in plays run with three wide receivers on the field. As a whole, Tennessee ran the ball on plays with three or more receivers on 21.9 percent of their rushing plays this season. The Titans called a rushing play out of 16 different formations this season, with the majority (107) coming from 12 personnel, most of which naturally brought extra defenders into the box. Exotic Smash Mouth, indeed.

6) Melvin Gordon, San Diego Chargers (4.69 yards per carry)

Rather surprisingly, Melvin Gordon took 33.2 percent of his non-red zone carries when facing eight or more defenders in the box, fifth-highest in the NFL. You wouldn't expect this sort of extra defensive attention for Gordon considering his rookie season was such a disappointment, but it was clear he needed it after starting off as well as he did and amassing so much volume. His 22.7 touches per game trailed only Le'Veon Bell, Ezekiel Elliott and David Johnson at the position. 41.5 percent of the Chargers running plays this year came out of a grouping with three or more wide receivers on the field, but the rest of their run plays came with multiple tight ends or running backs on the field, including 17.4 percent out of 21 or 22 personnel. The drafting of fullback Derek Watt was one of the clearest signs that the Chargers were committed to helping Gordon succeed in his second season.

7) Spencer Ware, Kansas City Chiefs (4.53 yards per carry)

With Jamaal Charles essentially a non-factor for the Chiefs in 2016, the team needed to call on Spencer Ware to be their feature back. While he slowed down amid poor run blocking to close the season, Ware turned in 1,368 total yards in 14 games on the year. Ware saw eight or more defenders in the box on 20.2 percent of his non-red zone carries this season, ranking 16th out of 19 players with 35 or more carries against stacked boxes. The Chiefs only ran out of 11 personnel on 35.3 percent of their plays, but ran out of 15 different groupings on the season. With that approach, defenses struggle to pay extra attention to just one player, even though the Chiefs are a run-heavy team. Either way, Ware was a steady runner against stacked boxes, ranking seventh-best in yards per attempt with just five runs of 10-plus yards and only two of 15-plus.

8) Jonathan Stewart, Carolina Panthers (4.51 yards per carry)

The running game was something of a disappointment for the Carolina Panthers this season, and they fell from the second-highest run play percentage in 2015 to eighth in 2016 amid more negative game scripts. Jonathan Stewart ran against an eight-plus man box on 33.1 percent of his non-red zone carries, the sixth-most among running backs with 35-plus carries against stacked fronts. The Panthers ran out of the three-wide receiver set on 43 percent of their run plays this season, but a number of their other jumbo packages invite extra defenders into the box. Over 26 percent of the Panthers run plays featured two backs (often Stewart and fullback Mike Tolbert) on the field. The threat of Cam Newton as a rusher also requires teams to respect an extra running threat and dedicate more resources to stopping it. Stewart still showed an ability to beat heavy defensive fronts, as he busted three plays of 20-plus yards against them. Yet, the Panthers should still explore adding additional talented young options to their backfield, especially for when Stewart misses his annual stretch with an injury or in the event he becomes a cap casualty.

9) Latavius Murray, Oakland Raiders (4.27 yards per carry)

Oakland aimed to run the ball more this season and they accomplished that, jumping from 25th in 2015 to 15th in run play percentage this year. Still, it is rather surprising to see Latavius Murray check in with 43.2 percent of his non-red zone carries coming against eight-plus defenders in the box, given how impressive their passing attack was this season. Oakland ranked 10th in plays run with three wide receivers on the field, and ran out of that package on 46.7 percent of their rushing plays. Perhaps on the majority of his other runs out of heavier offensive fronts is where he saw the most stacked boxes, or maybe he really is a focus of opposing defensive coordinators. Either way, Murray's 4.27 yards per carry against eight-plus defenders in the box was steady, and he only broke two runs of 15-plus yards.

10) Lamar Miller, Houston Texans (4.23 yards per carry)

Lamar Miller faced a stacked box on 22.6 percent of his non-red zone carries (13th out of 19) in 2016. While that's not one of the highest rates, it is notable when you consider what kind of formations the Texans often deployed. Houston ranked eighth in plays run with three wide receivers on the field and a whopping 48 percent of their run plays came out of those packages. Defenses typically can't reasonably stack the box when there are more than two wide receivers on the field. That just goes to show you what little respect the opposition had for quarterback Brock Osweiler. Not completely off the hook, Miller was only reasonably effective in his first true workhorse season, and clearly worn down under the workload by the end of the year. The 2016 free agent addition only broke one run of 15-plus yards against stacked fronts despite his explosive reputation heading into this season.

Four bonus notes:

David Johnson ranked just 17th with 3.12 yards per carry against stacked boxes with just one carry of 10-plus yards. Given how historically dominant his 2016 campaign was, it is more than a little interesting to find him so low in this metric. However, he saw the fewest percentage (18.4 percent) of his non-red zone carries against eight-plus defenders in the box. This is likely due to the Cardinals calling 52.1 percent of their run plays out of the three-wide receiver set.

LeGarrette Blount faced an eight-plus man box on 39 percent of his non-red zone carries, ranking fourth-highest. This is an example of where context matters, as Blount's figure isn't so high because teams are more worried about him than Tom Brady. Blount's numbers are inflated because he runs out of the rarely seen I-formation more (121) than any other package. Yet, this can at least dispense of the idea he constantly gets free room to work. Blount took three carries for 20-plus yards against a stacked box.

Todd Gurley's 2.94 yards per carry was the second-lowest, besting only Doug Martin's 2.73. The Rams running back faced a stacked box on 26.3 percent of his attempts (11th out of 19), despite the Rams running out of 11 personnel on 45.9 percent of their run plays. Narrative would have told you he'd be even higher, but much of Gurley's lost season can be placed at the feet of an overall dysfunctional Los Angeles offense.

Jordan Howard struggled with just 3.36 yards per carry against eight-plus defenders in the box. He also faced a stacked front on 26.4 percent of his non-red zone carries. Howard produced most of his big runs out of the shotgun (7.1 yards per carry) and the pistol (6.9 yards per carry). While this might be nothing to sound the alarm over, it's a footnote to consider as he heads into 2017 after a shockingly dominant rookie season that will certainly earn him more defensive attention.